no detailed study of the Kepler data; the survey papers mention it, but a survey is not a study
Variable at very low level; the longer Kepler runs show a chaotically varying object. Gaia G = 10.589 at ~240 pc, M_G = 3.68 -- the brightest and nearest star in the project, and at log g ~5.13 an inflated, helium-enriched object well above the EHB, in the same territory as Largo. The Kepler photometry has never been published.
| survey / pre-Kepler mention | Lei et al. 2018, ApJ 868, 70 -- a LAMOST catalogue analysis, not a study of this star, and it uses no Kepler data. It gives Teff 30560 +- 260 K, log g 5.100 +- 0.040, log N(He)/N(H) -1.590 +- 0.040 from SYNSPEC/TLUSTY NLTE models through XTgrid, which is the value the table quotes -- but the star itself is UNPUBLISHED. |
| atmospheric parameters | Lei et al. (2018): 30560 +- 260 K, log g 5.100 +- 0.040, log N(He)/N(H) -1.590 +- 0.040. That Teff is ~1800 K hotter than all five spectra fitted here, which agree among themselves to 837 K |
| the spectrum behind it | Lei et al. worked from LAMOST spectra; all five DR11 epochs are here, with a WHT, a Bok and a KPNO 4m mean besides. |
| observation | telescope | date | n | S/N | FWHM [Å] | Teff [K] | log g | log n(He)/n(H) | residual | χ² |
|---|---|---|---|---|---|---|---|---|---|---|
| BOK | bok / bcspeclamps | 2000-06-24 | 9 | 1912.0 | 9.00 | 28378 ± 119 | 5.096 ± 0.015 | -1.50 ± 0.01 | 1.25% | 7.37 |
| KPNO | kp4m / test | 2010-08-12 | 14 | 623.3 | 1.60 | 29215 ± 101 | 5.085 ± 0.012 | -1.79 ± 0.02 | 1.78% | 4.82 |
| LAMOST | LAMOST | 1 | 256.7 | 2.50 | 28584 ± 140 | 5.139 ± 0.015 | -1.55 ± 0.04 | 1.20% | 0.93 | |
| LAMOST-mean | LAMOST | 5 | 304.9 | 2.50 | 28827 ± 118 | 5.143 ± 0.015 | -1.58 ± 0.02 | 1.20% | 3.88 | |
| WHT ★ | WHT / ISIS blue arm | 2009-04-13 | 1 | 240.6 | 3.00 | 28631 ± 113 | 5.187 ± 0.014 | -1.61 ± 0.02 | 1.14% | 3.19 |
★ marks the observation adopted for the sample table — the one with the smallest residual, which is what says how well the model reproduces the spectrum. Signal-to-noise does not.
The line fit gives a temperature and a gravity but says nothing about size. Held at those parameters, the broadband spectral energy distribution has one free scale — the angular diameter — and the Gaia parallax turns that into a radius. Then M = gR²/G, which is linear in g: a tenth of a dex in gravity is 26 per cent in mass, so this is where the gravity scale bites hardest.
| distance [pc] | 241 |
| parallax error [%] | 0.8 (per cent; the mass error is twice this) |
| E(44−55) [mag] | 0.068 (0.060–0.076) |
| … the dust map | 0.0230 (SFD×disk(f=0.40)) |
| log Θ [rad] | -10.307 +0.004 −0.004 |
| R [R☉] | 0.264 +0.003 −0.003 |
| M [M☉] | 0.390 +0.049 −0.043 |
| L [L☉] | 42.1 +1.6 −1.5 |
Bamberg v25 ATLAS12 through the real filter curves, reddened by Fitzpatrick (1999) — its A(5500)/E(B−V) is 3.03, so this E(B−V) and the E(44−55) of Heber's group are the same number to under one per cent. Prescribed at 28631 K and log g 5.187 from WHT, with 39 of the fitted bands and reduced χ² 0.14. The gravity error carried into the mass is 0.050 dex — the scatter between telescopes, not the formal error, because the formal one would claim a two per cent mass.
Bands left out: Johnson:B, GALEX:NUV, GALEX:FUV, SDSS:g/SDSS:g', SDSS:i/SDSS:i', SDSS:r/SDSS:r', SDSS:u, WISE:W4, GAIA/GAIA3:G, GAIA/GAIA3:Gbp, GAIA/GAIA3:Grp, SDSS:g, SDSS:r, SDSS:i, SDSS:z, SDSS:u/SDSS:u', SDSS:z/SDSS:z', Johnson:U, Johnson:V, Cousins:U.
kpno/ is a copy of the fitprof22 working directory from data/spek/kepler/kpno/kic06848529, kept as it was run. It arrived holding its spectrum as sp.spek, the name fitk1 looks for, so the file is renamed kpno.spek here and its runfit20.dat points at the new name; the directory is an archive again and the 2010 fit is still reproducible. The original is untouched. The live directory is KPNO/, linked to the master. The 2010 fit reported nHe = 0.0000 +/- 0.0000, pinned at the top of its grid, so it is not a measurement. The KPNO 4m header gives 19:08:03 +42:19:38, about 5 arcmin from the J19076+4218 in the name -- the same offset Rosie's KPNO header shows, so these headers appear to carry the pointing rather than the star. LAMOST/ is the LAMOST DR11 fit of the same star, copied verbatim from share/lamost/J19076+4218 and marked "as_run" so fitk1 leaves it alone -- the two pipelines are not identical (see Lobelia/chidel.why). Its lei.out carries the published values, Lei et al. (2018): 30560 K, log g 5.10, log n(He)/n(H) -1.59. LAMOST-mean/ is a straight mean of all five DR11 epochs (MJD 56570, 57291 x2, 57920 x2), which the archive does not use -- it quotes the single best spectrum. The five agree to 10 km/s peak to peak, far inside the ~190 km/s resolution element, so no shifting was needed; that also means no orbital motion is detected here, though LAMOST cannot see much. wht/ and bok/ are copies of the fitprof22 working directories from data/spek/kepler/KepI (BD+42_3250_WHT and BD+42_3250_Bok), with the Bok mean frame bd+42_3250.fits brought in from KepI/Betsy beside it. Neither holds an sp.spek, so fitk1 does not read them. wht/ also carries a flux calibration set (fract, dered, twosp, test*) of the same kind as Largo's. BD+42 3250 = 2M1907+4218 = KIC 6848529 = Balbo: the WHT and Bok headers both give 19:07:40.5 +42:18:22, which is the J19076+4218 of the name. The KPNO 4m header gives 19:08:03 +42:19:38, about 5 arcmin away -- that header carries the pointing, not the star, exactly as Rosie's does. The three dated files in bok/ (13jun08f, 27jul08f, 28jul08f) are single 2008 exposures of 36-42 s; bd+42_3250.spek beside them is the mean of nine from 2000-06-24 and is what BOK/ uses.